Avalanche photodiodes (APDs) are widely utilized for fiber-optic communications due to higher sensitivity benefitting from carrier multiplication mechanism. Traditional III-V APD receivers offer more than 6 dB sensitivity improvement up to 10 Gb/s data rate when compared to PIN photodiodes (PD). However, InP-based APDs show limited gain-bandwidth product and high multiplication noise due to large k-factor, i.e., ratio of impact ionization coefficients. Silicon (Si)-based APDs have been demonstrated to be the best device for high-speed communication applications, where germanium (Ge) is used as absorption material. Ge material is an indirect band-gap material. When under tensile strain, both Ge L-band and r-band shrink, but the direct Γ-band shrinks faster and becomes a direct band-gap material, thereby the Ge absorption coefficient to longer-wavelength incident light increases. Additionally, Ge material can be utilized in APDs for C-band applications (around 1500 nm or 1550 nm) and fiber-to-the-home (FTTH) applications (around 1577 nm). Typically C-band application applies industrial standard, where the operational temperature ranges from −40° C. to 85° C., while the operational temperature range of FTTH application is usually from −20° C. to 75° C. With wavelength around 1550 nm and 1577 nm, the Ge material absorption coefficient is sensitive to temperature, and GeSi APD sensitivity deteriorates seriously when operating in a lower-temperature environment instead of room temperature.
One approach to maintain Ge PD performance at lower temperature is to mount a 30Ω resistor on the top-surface of a 6-pin transistor outline (TO)-header, as illustrated in FIG. 1. When a 3.3V bias voltage is applied on the resistor, the heat generated in the resistor can heat up the TO-header and increase TO temperature by about tens of degrees depending on consumption power. Accordingly, the sensitivity performance of Ge/Si APDs can be improved to meet specified requirements. Since there is a gap of hundreds of microns between the resistor and Ge/Si APD chip, a time period of typically tens of seconds is required to transfer heat from the resistor to the Ge region via TO-header, as shown in FIG. 1. As a result, the efficiency and response speed of this approach is too low for practical applications.